KR101861461B1 - Systems and methods for joint handover of user equipment and secondary cell group in 3gpp lte dual connectivity - Google Patents

Abstract

The system and method provide a federated handover process wherein the user equipment (UE) and the at least one secondary node are kept connected to each other and handed over together from the first master node to the second master node. Thus, a reset procedure by at least one secondary node is avoided.

Description

TECHNICAL FIELD [0001] The present invention relates to a system and a method for a combined handover between a user equipment and a secondary cell group in 3GPP LTE dual connectivity,

Related application

This application claims the benefit of U.S. Provisional Application No. 61 / 953,614 (Attorney Docket No. P64438Z) filed March 14, 2014, the entirety of which is incorporated herein by reference. Request the priority of § 119 (e).

Technical field

The present invention relates to a wireless communication network. In particular, the present invention relates to a system and method for providing handover for a user equipment (UE) operating in dual connectivity in a wireless communication system.

1 is a block diagram of a communication network operating in dual connectivity according to one embodiment.
2 is a block diagram of a communication network illustrating an exemplary handover scenario in dual connectivity according to one embodiment.
3 is a sequence diagram illustrating a process for a joint handover according to one embodiment.
4 is an exemplary diagram of a mobile device according to a particular embodiment.

A detailed description of a system and method according to an embodiment of the present invention is provided below. While a number of embodiments have been described, the invention is not limited to any one embodiment, but instead includes numerous alternatives, modifications, and equivalents. In addition, while a number of specific details are set forth in the detailed description that follows to provide a thorough understanding of the embodiments disclosed herein, some embodiments may be practiced without some or all of these details. Moreover, for clarity, certain technical materials known in the relevant art are not described in detail in order to avoid unnecessarily obscuring the present invention.

The systems and methods disclosed herein reduce the signaling overhead during handover in a heterogeneous network. In a third term partnership project (3GPP) long term evolution (LTE) system, dual connectivity means that a UE (e.g., a wireless device such as a cellular phone) (E. G., A master node and a secondary node) connected to each other by at least two different network nodes (e. G., An X2 interface). As will be described in detail below, when the moving UE is handed over from the coverage area of one master node to the coverage area of another master node, existing systems have disconnected the UE from each node involved in dual connectivity. The specific embodiment described herein provides a cooperative handover process wherein the UE and the at least one secondary node are kept connected to each other and handed over together from the first master node to the second master node. Thus, a reset procedure by at least one secondary node is avoided.

In a 3GPP radio access network (RAN) LTE system, a node is an evolved universal terrestrial radio access network (E-UTRAN) Node B (also typically an evolved Node B, an enhanced Node B, eNodeB, or eNB) and radio network controllers (RNCs) that communicate with a wireless device known as a user equipment (UE). A downlink (DL) transmission may be a communication from a node (e.g., an eNB) to a wireless device (e.g., a UE), and an uplink (UL) transmission may be from a wireless device to a node.

In homogeneous networks, a node, also referred to as a macro node, may provide basic wireless coverage for wireless devices in the cell. This cell may be an area in which the wireless device is operable to communicate with the macro node. The heterogeneous network may be used to handle increased traffic load on a macro node due to increased usage and functionality of the wireless device. The heterogeneous network may be a low power node (small cell, small-eNB, micro-eNB, pico-eNB, femto-eNB, etc.) that can be deployed in a less well- , Or a hierarchy of planned high power macro nodes (macro-eNB or macrocell) overlapping layers of the home eNB [HeNB]. A low power node (LPN) is generally referred to as a "low power node ", a small node, or a small cell.

Macro nodes can be used for default coverage. A low power node can be used to fill a coverage hole at the boundary between the geographical coverage area (i.e., cell) of the macro node and the coverage area of the macro node. Low power nodes may also be used to increase capacity in high usage areas and to increase indoor coverage where building structures interfere with signal transmission.

As used herein, the terms "node" and "cell" are intended to be synonymous and refer to a wireless transmission point operable to communicate with a number of user equipments, such as an eNB, a low power node, or another base station.

Dual connectivity refers to an operation in which a given UE consumes radio resources provided by at least two different nodes connected to a non-ideal backhaul. For example, Figure 1 is a block diagram of a communication network 100 operating in dual connectivity according to one embodiment. The network 100 includes a macrocell 110 configured to communicate user data 112 to a UE 114 using a first carrier frequency F1 and a user cell 110 using a second carrier frequency F2, To the UE 114. The small cell 116 may be configured to communicate with the UE 114 via a communication link (e.g. Macrocell 110 and small cell 116 communicate with each other via non-ideal backhaul interface 120 (e.g., X2 interface). The dual connectivity shown in Figure 1 provides inter-node radio resource aggregation (or inter-site carrier aggregation) to increase per-user throughput. Dual connectivity allows mobility management to be maintained on the macro layer while aggregating small cells to provide extra user plane capacity to increase throughput. The radio bearers that carry the user data 112 and 118 may be used only to allocate resources of only the macrocell 110 or only the small cell 116, depending on whether increased coverage, offload, May be used, or both may be aggregated. Maintaining a mobility anchor in the macrocell 110 may help to reduce the signaling overhead towards the core network.

Nodes involved in dual connectivity for UE 114 (e.g., macrocell 110 and small cell 116) may assume different roles, which are not necessarily dependent on the power class of the node . For example, one node may act as a master node, and one or more additional nodes may act as a secondary or slave node. Generally, though not always, the macrocell 110 may perform the function of the master eNB (MeNB), and the small cell 116 may perform the function of the secondary eNB (SeNB). MeNB is terminated with at least S1-MME, which is an interface for a control plane protocol to a mobility management entity (MME) in the core network. Thus, the MeNB acts as a mobile anchor for the UE 114 towards the core network. The group of serving cells associated with this MeNB may be referred to as a master cell group (MCG) in this specification. Unlike the MeNB, the SeNB is an eNB that provides additional radio resources for the UE. The group of serving cells associated with this SeNB may be referred to as a secondary cell group (SCG) in this specification.

The specific embodiments disclosed herein reduce the signaling overhead during handover of the UE in dual connectivity where SeNB is expected to evolve in a dedicated spectrum. Handover may occur frequently when a small cell (e.g., small cell 116) due to a smaller coverage area is deployed in the network as compared to the coverage area of the macrocell. In a dual connectivity deployment, the handover of the UE 114 may occur as inter-frequency or intra-frequency handover. MeNB to MeNB (Carrier frequency (F1)) handover and SeNB to SeNB (Carrier frequency (F2)) handover are in-frequency handovers. MeNB to SeNB handover (carrier frequency (F1) to carrier frequency (F2)) and SeNB to MeNB handover (carrier frequency (F2) to carrier frequency (F1)) are inter-frequency handovers.

2 is a block diagram of a communication network 200 illustrating an exemplary handover scenario in dual connectivity according to one embodiment. The communication network includes a UE 210 served by a split bearer via serving MeNB 212 and SeNB 213. [ The arrow 220 shown in FIG. 2 indicates the direction in which the UE 210 is moving. In this example, the UE 210 moves from the coverage area 216 of the serving MeNB 212 to the coverage area 218 of the target MeNB 214 while remaining in the coverage area 222 of the SeNB 213. The SeNB 213 provides an interconnection between the serving MeNB 212 and the target MeNB 214 (e.g., via the X2 interface). The UE 210 periodically measures the strength of the signal received from the serving MeNB 212. The UE 210 reports measurements to the serving MeNB 212. As the UE 210 approaches the edge of the coverage area 216, the signal strength decreases and the serving MeNB 212 determines to handover the UE 210 to the target MeNB 214.

In general, handover in dual connectivity may not be desirable due to a large number of overhead messages, such as radio resource control (RRC) signaling messages communicated during handover. In addition, the handover may also include additional overhead, including random access, uplink synchronization, and physical layer reconfiguration when UE 210 enters coverage area 218 of target MeNB 214. [ Thus, considerable control signaling overhead can be achieved over the RAN (e.g., MeNB 212, 214, SeNB 213, or other node) and the core network infrastructure (e.g., MME in evolved packet core Serving gateway (S-GW)). Reducing handover and / or handover signaling in a heterogeneous network using dual connectivity, in accordance with the embodiments disclosed herein, can significantly reduce the overhead for the core network and / or RAN.

In one embodiment, the serving MeNB 212 may perform a federated handover procedure to move the UE 210 and the SeNB 213 together with a new MCG associated with the target MeNB 214 to reduce signaling overhead and delay time . The signaling overhead is reduced, for example, by eliminating the separate process of disconnecting and reconnecting the UE 210 to the SeNB 213. [ The time delay is reduced, for example, by eliminating extra delays in the individual handover and SeNB change processes.

FIG. 3 is a sequence diagram illustrating a process 300 for federated UE handover and SeNB modification in accordance with one embodiment. 3, the combined UE handover and SeNB modification process 300 involves the UE 210, the SeNB 213, the serving MeNB 212, and the target MeNB 214 shown in FIG. 2 . UE 210 is served by a split bearer via Serving MeNB 212 and SeNB 213 before the illustrated process 300 begins. Process 300 also includes an MME 310 within the core network. Those skilled in the art will recognize that other core network elements may also be involved in the federated UE handover and SeNB modification process 300 in certain embodiments.

The UE 210 periodically measures a reference signal received power (RSRP) or a reference signal received quality (RSRQ) of the MeNB-UE link with the serving MeNB 212. The UE 210 also periodically measures the RSRP or RSRQ of the signal received from the target MeNB 214. After a time interval (e.g., set by a time to trigger (TTT) timer) that is selected to decrease the measurement event and to reduce unnecessary handover (e.g., a "ping pong" effect), the UE 210 sends a measurement report signal 312 to the RRC entity at the serving MeNB 212. In response, the serving MeNB 212 sends a "handover request to keep SCG" message 314 to the target MeNB 214 via the X2 interface.

After receiving the handover request message 314 holding the SCG, the target MeNB 214 prepares for the handover of the UE 210 and the addition of the SeNB 213 to the MCG of the target MeNB 214, And acknowledges the acceptance of the request by sending a handover (HO) response message 316 to the serving MeNB 212 over the network. In response, the serving MeNB 212 sends a modified RRC connection reconfiguration message 318 to the UE 210. [ The RRC connection reconfiguration message 318 indicates the start of the split bearer handover of the UE 210 to the target MeNB 214 without disconnecting the connection between the UE 210 and the SeNB 213. [ UE 210 then initiates a random access procedure with target MeNB 214. < RTI ID = 0.0 > The random access procedure 320 may establish a connection between the UE 210 and the target MeNB 214 (e.g., assigning an uplink radio resource to allow the UE 210 to transmit user data to the target MeNB 214) If a connection is established, the UE 210 sends an RRC connection reconfiguration complete message 322 to the target MeNB 214.

In order to change the MCG of the SeNB 213, the serving MeNB sends an "SCG Keep-MCG Change Command" message via the X2 interface to indicate that the target MeNB 214 will be the new MeNB for the UE 210 (324) to the SeNB (213). In response, SeNB 213 sends a "Keep SCG - MCG Change Responses" message 326 to Serving MeNB 212 and Target MeNB 214 to acknowledge the change of MeNB. The serving MeNB 212 sends a sequence number (SN) status transfer and data forwarding message 328 to the target MeNB 214 and the target MeNB 214 and the MME 310 send a path switch request and response message (330). The target MeNB 214 completes the process 300 by sending a UE context release message 332 to the serving MeNB. The target MeNB 214 becomes a new serving MeNB for the UE 210 and the SeNB 213 changes the MCG without detaching from the UE 210. [ Thus, the UE 210 is served by the split bearer via the target MeNB 214 (now serving MeNB) and SeNB 213. [

A number of messages shown in FIG. 3 are provided below as examples. Some examples are the 3GPP Technical Specification (TS) 36.331, V12.0.0 (2013-12) (TS 36.331); And 3GPP TS 36.423, V12.0.0 (2013-12) (TS 36.423).

In one embodiment, the RRC connection reconfiguration message 318 shown in FIG. 3 includes an additional " CellToKeeplist "field, as shown in the following abstract syntax notation one (ASN.1) This is a modification of the RRCConnectionReconfiguration message in TS 36.331.

RRCConnectionReconfiguration message

The "CellToKeeplist" field in the sample ASN.1 code is optionally present and needs to be on in case of a dual connectivity handover while keeping the cell in the SCG and merely changing the cell in the MCG. Otherwise, "CellToKeeplist" is not present in the RRCConnectionReconfiguration message.

In one embodiment, the RRC connection reconfiguration complete message 332 shown in FIG. 3 is a modification of the RRCConnectionReconfigurationComplete message of TS 36.331 with the additional "CellToKeeplist" field described above, as shown in the following exemplary ASN.1 code .

RRCConnectionReconfiguration message

In one embodiment, a handover request to maintain the SCG message 314, as shown in FIG. 3, is described in the following Tables 1A and 1B. See section 9.0 of TS 36.432.

[Table 1A]

[Table 1B]

In one embodiment, the SCG Hold-MCG Change command message 324 shown in FIG. 3 is described by the following Table 2A and Table 2A. See section 9.0 of TS 36.432.

[Table 2A]

[Table 2B]

In one embodiment, the SCG Hold-MCG Change Response message 326 shown in FIG. 3 is described below by Tables 3A and 3B. See section 9.0 of TS 36.432.

[Table 3A]

[Table 3B]

In an embodiment, the message type information element (IE) in section 9.2.13 of TS 36.423 includes "Handover Requests to Maintain SCG" corresponding to Table 2A and Table 3A And a semantic description of "SCG maintenance-MCG change"

[Table 4]

4 is an exemplary illustration of a mobile device, such as a UE, mobile station (MS), mobile wireless device, mobile communication device, tablet, handset, or other type of wireless communication device. A mobile device may include a base station (BS), an eNB, a baseband unit (BBU), a remote radio head (RRH), a remote radio equipment (RRE), a relay station , A radio equipment (RE), or other type of wireless wide area network (WWAN) access point. The mobile device may be configured to communicate using at least one wireless communication standard, including 3GPP LTE, WiMAX, high speed packet access (HSPA), Bluetooth, and Wi-Fi. The mobile device may communicate using an individual antenna for each wireless communication standard or a shared antenna for multiple wireless communication standards. The mobile device may communicate in a wireless local area network (WLAN), a wireless personal area network (WPAN), and / or a WWAN.

Figure 4 also provides a diagram of a microphone and one or more speakers that can be used for audio input and output from a mobile device. The display screen may be another type of display screen, such as a liquid crystal display (LCD) screen or an organic light emitting diode (OLED) display. The display screen may be configured as a touch screen. The touch screen may use capacitive, resistive, or other types of touch screen technology. The application processor and graphics processor may be coupled to the internal memory to provide processing and display functions. A non-volatile memory port may also be used to provide data input / output options to the user. A non-volatile memory port may also be used to extend the memory capabilities of the mobile device. The keyboard may be integrated with the mobile device or wirelessly connected to the mobile device to provide additional user input. A virtual keyboard may also be provided using the touch screen.

Additional illustrative Example

The following is an example of a further embodiment.

Example 1 is an evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) that includes a processor, a wireless transceiver for communicating with a user equipment (UE), and a processor. The processor establishes a connection to the UE via the radio transceiver as a serving master eNB (MeNB), the UE is in dual connectivity with the serving MeNB and the secondary eNB (SeNB), determines to handover the UE from the serving MeNB to the target MeNB And to handover both the UE and the SeNB to the target MeNB in response to the determination.

Example 2 includes the subject matter of Example 1, wherein the radio transceiver is configured to receive from the UE a measurement report indicating the strength of the signal received by the UE from at least the eNB. The processor is further configured to process the measurement report to determine that the UE is moving from a first cell coverage area corresponding to the serving MeNB to a second cell coverage area corresponding to the target MeNB. In response, the processor determines to handover the UE from the serving MeNB to the target MeNB.

Example 3 comprises an object of any of Examples 1 to 2, wherein the measurement report includes a reference signal received power (RSRP) or a reference signal reception quality (RSRQ).

Example 4 includes the subject matter of any of Examples 1 to 3, wherein in order to handover both UE and SeNB to the target MeNB, the processor sends a handover request to the target MeNB - the handover request is sent to the SeNB Instructing the target MeNB to maintain a corresponding secondary cell group (SCG), - sending a Radio Resource Control (RRC) connection reconfiguration message to the UE via the wireless transceiver, wherein the RRC connection reconfiguration message is maintained in the SCG Lt; RTI ID = 0.0 > a < / RTI >

Example 5 includes the claimed subject matter of Example 4 wherein the processor includes a list of cells to keep in the SCG and instructions to change the SeNB to a master cell group (MCG) corresponding to the MeNB SeNB < / RTI >

Example 6 includes the subject matter of Example 5, wherein the processor receives a response to the command from the SeNB; Transmitting a sequence number status transfer and a data forwarding message to the target MeNB; And to receive the UE context deactivation message from the target MeNB.

Example 7 includes an object of any of Examples 1 to 6, wherein the serving MeNB is configured to communicate with SeNB and MeNB via a non-ideal backhaul interface X2.

Example 8. A user equipment (UE) comprising a first evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) and a plurality of radio transceivers for receiving user data via a split bearer from a second eNB. The UE periodically measures a reference signal received power (RSRP) or a reference signal reception quality (RSRQ) of the link with the first eNB; Transmit an RSRP or RSRQ measurement report to a first eNB through a first radio transceiver of the plurality of radio transceivers; Receiving, from the first eNB, a message indicating the start of a split bearer handover of the UE from the first eNB to the third eNB; And in response to the message, a circuit for maintaining a connection to the second eNB during a split bearer handover of the UE from the first eNB to the third eNB.

Example 9 includes the subject matter of Example 8 wherein the circuit determines the measurement event trigger based on the measured RSRP or RSRQ for the link with the first eNB and before sending the RSRP or RSRQ measurement report to the first eNB And is further configured to wait for a predetermined time to trigger (TTT) timer to expire.

Example 10 comprises the subject matter of any of Examples 8 to 9, wherein the message indicating initiation of the split bearer handover represents a list of cells to maintain in the secondary cell group (SCG) corresponding to the second eNB Lt; RTI ID = 0.0 > (RRC) < / RTI >

Example 11 includes the subject matter of any one of Examples 8-10, wherein in response to receiving the RRC Connection Reconfiguration message, the circuit is configured to perform a random access procedure to establish a connection between the UE and the third eNB, And to communicate with the third eNB through a second wireless transceiver of the wireless transceiver.

Example 12 includes an object of any one of Examples 8-11 wherein the UE may be an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, an embedded memory, a non-volatile memory port, Or the like.

Example 13 is a node for communicating with a wireless communication system. A node comprises: one or more processors; one or more processors associating nodes with a secondary cell group (SCG) of a wireless communication system; Establishing a connection with a user equipment (UE); Collaborate with a first node in a first master cell group (MCG) to provide dual connectivity to the UE; Receive a command from a first node to change a dual connectivity of the UE from a first node in a first MCG to a second node in a second MCG; Readable storage medium having stored thereon program code for causing a UE to maintain a connection with a UE to provide dual connectivity to the UE and to change from a collaboration with a first node to a collaboration with a second node, Lt; / RTI > computer program product.

Example 14 includes the claimed subject matter of Example 13, wherein the instructions received from the first node in the first MCG comprise a list of cells to maintain in the SCG.

Example < RTI ID = 0.0 > 15 < / RTI > includes the claimed subject matter of any one of Examples 13-14, wherein in response to a command received from a first node in the first MCG, 1 MCG and the second node in the second MCG.

Example 16 comprises an object of any of Examples 13-15 wherein the node communicates with at least one of a first node in a first MCG and a second node in a second MCG via a non-ideal backhaul interface X2 .

Example 17 includes the steps of transmitting a request to handover a UE from a first master node to a second master node while maintaining a secondary node connected to the UE, 1. A method comprising: sending a message to a UE for detachment from a master node and for connection with a second master node; performing a random access procedure to establish a connection between the UE and a second master node; And ending the connection between the nodes.

Example 18 includes the claimed subject matter of Example 17, and after establishing a connection between the UE and the second master node, while maintaining the connection between the secondary node and the UE, the first master cell group corresponding to the first master node To a second master cell group corresponding to the second master node, to the secondary node.

Example 19 includes the claimed subject matter of any one of Examples 17 to 18, comprising: receiving from a UE a measurement report comprising a reference signal received power (RSRP) or a reference signal receiving quality (RSRQ) And sending a request to handover the UE from the first master node to the second master node.

Example 20 comprises the subject matter of any of Examples 17 to 21, wherein transmitting a request to handover a UE from a first master node to a second master node comprises the steps of: And transmitting the list.

Example 21 comprises the subject matter of any of Examples 17 to 22, wherein transmitting a request to handover a UE comprises sending the request via a non-ideal backhaul interface X2.

Example 22 is a method comprising establishing a connection to a user equipment (UE) via a wireless transceiver as a serving master enhanced Node B (MeNB). The UE is in dual connectivity with the serving MeNB and the secondary eNB (SeNB). The method further comprises determining to handover the UE from the serving MeNB to the target MeNB, and in response to the determination, performing handover of both the UE and the SeNB to the target MeNB.

Example 23 comprises the steps of: receiving from a UE a measurement report indicating the strength of a signal received by the UE from at least an eNB, including the claimed subject matter of Example 22; and determining whether the UE receives a target MeNB from the first cell coverage area corresponding to the serving MeNB Processing the measurement report to determine that it is moving to a second cell coverage area corresponding to the target cell, and in response, determining to handover the UE from the serving MeNB to the target MeNB.

Example 24 includes the subject matter of any of Examples 22-23, wherein the measurement report includes a reference signal received power (RSRP) or a reference signal reception quality (RSRQ).

Example 25 comprises the subject matter of any one of Examples 22 to 24, wherein in order to handover both the UE and the SeNB to the target MeNB, the method comprises the steps of: transmitting a handover request to the target MeNB, And instructing the target MeNB to maintain a secondary cell group (SCG) corresponding to the RRC connection reconfiguration message, and sending a Radio Resource Control (RRC) connection reconfiguration message to the UE via the wireless transceiver, The message includes a field indicating a list of cells to keep in the SCG.

Example 26 includes sending a command to the SeNB that includes the subject matter of Example 25 and includes a list of cells to keep in the SCG and an instruction to change the SeNB to the master cell group (MCG) corresponding to the MeNB .

Example 27 includes the claimed subject matter of Example 26 and includes receiving from the SeNB a response to the command, transmitting a sequence number status propagation and data forwarding message to the target MeNB, receiving from the target MeNB a UE Context Release message The method comprising the steps of:

Example 28 includes the steps of receiving user data via a split bearer from a first evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (eNB) and a second eNB, and transmitting the reference signal received power of the link with the first eNB Periodically measuring RSRP or RSRQ; transmitting an RSRP or RSRQ measurement report to the first eNB via the first radio transceiver; and transmitting the RSRP or RSRQ measurement report from the first eNB to the first eNB, Comprising the steps of: receiving a message indicating initiation of a split bearer handover of the UE to the eNB; and maintaining a connection to the second eNB during a split bearer handover of the UE from the first eNB to the third eNB in response to the message .

Example 29 comprises the steps of determining the measurement event trigger based on the measured RSRP or RSRQ for the link with the first eNB, including the claimed subject matter of Example 28, expiration before sending the RSRP or RSRQ measurement report to the first eNB, And waiting for a predetermined time-to-trigger (TTT) timer.

Example 30 comprises the subject matter of any of Examples 28 to 29, wherein the message indicating the initiation of the split bearer handover represents a list of cells for holding in the secondary cell group (SCG) corresponding to the second eNB Lt; RTI ID = 0.0 > (RRC) < / RTI >

Example 31 includes the subject matter of Example 30, wherein in response to receiving the RRC Connection Reconfiguration message, the method further comprises transmitting the RRC Connection Reconfiguration message via the second radio transceiver to perform a random access procedure for establishing a connection between the UE and the third eNode B 3 < / RTI > eNB.

Example 32 includes associating a node with a secondary cell group (SCG) of a wireless communication system, establishing a connection with a user equipment (UE), and establishing a connection with a first master cell group Receiving a command from a first node to change a dual connectivity of the UE from a first node in a first MCG to a second node in a second MCG; And maintaining a connection with the UE to provide dual connectivity to the UE and changing from collaboration with the first node to collaboration with the second node.

Example 33 includes the subject matter of Example 32, wherein the instructions received from the first node in the first MCG comprise a list of cells to maintain in the SCG.

Example 34 includes an object of any of Examples 32 to 33, wherein in response to receiving an instruction from a first node in a first MCG, a message including a list of cells to maintain in the SCG is transmitted to a first MCG To the first node in the first MCG and to the second node in the second MCG.

Example 35 is an apparatus comprising means for performing the same method as in any of Examples 17 to 34. [

Example 36 is a machine-readable storage medium comprising machine-readable instructions for implementing the method as in any one of Examples 17-34.

The various techniques disclosed herein or specific aspects or portions thereof may be embodied in a program embodied in a tangible medium such as a floppy diskette, CD-ROM, hard drive, non-volatile computer readable storage medium, or any other machine- Code (i. E., Instructions), wherein when the program code is loaded into a machine such as a computer and executed, the machine becomes a device for implementing various techniques. In the case of program code execution on a programmable computer, the computing device may include a processor, a storage medium readable by the processor (including volatile and nonvolatile memory and / or storage elements), at least one input device, and at least one output Device. Volatile and nonvolatile memory and / or storage elements may be RAM, EPROM, flash drive, optical drive, magnetic hard drive, or other medium for storing electronic data. The eNB (or other base station) and the UE (or other mobile station) may also include a transceiver component, a counter component, a processing component, and / or a clock component or a timer component. One or more programs that implement or utilize the various techniques described herein may use an application programming interface (API), reusable controls, and the like. Such a program may be implemented in a high-level procedure or object-oriented programming language for communicating with a computer system. However, the program (s) may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and may be combined with a hardware implementation.

It is to be understood that the plurality of functional units described herein may be implemented as one or more modules or components, which are terms used to more particularly emphasize their implementation independence. For example, a module or component may include a very large scale integration (VLSI) circuit or off-the-shelf semiconductors such as gate arrays, logic chips, transistors, or other discrete components As shown in FIG. The modules or components may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, and the like.

The modules or components may also be implemented in software for execution by various types of processors. Identified components of executable code may include, for example, one or more physical or logical blocks of computer instructions that may be organized as an object, procedure, or function. Nonetheless, the identified modules or executable files of the components need not be physically co-located, but when logically combined together, they may include modules or components and may be implemented in different Lt; RTI ID = 0.0 > location. ≪ / RTI >

Indeed, a module or component of an executable code may be a single instruction, or multiple instructions, and may even be distributed across different code segments, across different programs, and across multiple memory devices. Similarly, operational data may be identified and illustrated herein within modules or components, embodied in any suitable form, and organized into any suitable type of data structure. Operational data may be collected as a single data set or distributed across different locations including across different storage devices and may be present, at least in part, as electronic signals on a system or network. The module or component may be passive or active, including an agent operable to perform the desired function.

Reference throughout this specification to "exemplary " means that a particular feature, structure, or characteristic described in connection with the examples is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in the examples " in various places throughout this specification are not necessarily all referring to the same embodiment.

As used herein, a plurality of items, structural elements, composition elements, and / or materials may be conveniently presented in a common list. However, these lists should be interpreted as if each member of the list is individually identified as a separate and unique member. Thus, no individual member of such a list should be interpreted as a de facto equivalent of any other member of the same list based solely on its presentation in a common group without the contrary indication. In addition, various embodiments and examples of the invention may be mentioned herein with alternative examples for their various components. It should be understood that such embodiments, examples, and alternatives should not be interpreted as substantially equivalent to each other, but should be considered as separate autonomous representations of the present invention.

Although a few details have been set forth for clarity, it will be apparent that certain changes and modifications may be made without departing from the principles. It should be noted that there are many alternative ways of implementing all of the processes and devices described herein. Accordingly, the embodiments of the present invention should be considered as illustrative rather than limiting, and the present invention is not limited to the details provided herein, but may be modified within the scope and equivalence of the appended claims.

It will be understood by those skilled in the art that numerous changes may be made in the details of the above-described embodiments without departing from the underlying principles of the invention. Accordingly, the scope of the present invention should be determined only by the following claims.

100: communication network 110: macro cell
112: User data 114: UE
116: small cell 118: user data
120: non-ideal backhaul interface 200: communication network
212: Serving MeNB 213: SeNB
216: Coverage area 218: Coverage area

Claims (25)

In an evolved universal terrestrial radio access network (E-UTRAN) Node B (eNB)
A wireless transceiver for communicating with a user equipment (UE)
A processor,
The processor
Establishing a connection to the UE via the radio transceiver as a serving master eNB (MeNB), the UE being in dual connectivity with the serving MeNB and the secondary eNB (SeNB)
Determine to handover the UE from the serving MeNB to a target MeNB,
And in response to the determination, to handover both the UE and the SeNB to the target MeNB,
In order to handover the SeNB to the target MeNB, the processor sends a handover request to the target MeNB instructing the target MeNB to maintain a secondary cell group (SCG) corresponding to the SeNB (A command) including a list of cells to be maintained in the SCG and an instruction to change the SeNB to a master cell group (MCG) corresponding to the target MeNB, to the SeNB Configured to transmit
eNB.
The method according to claim 1,
Wherein the wireless transceiver is configured to receive from a UE a measurement report indicating the strength of a signal received by the UE from at least the eNB,
Processing the measurement report to determine that the UE is moving from a first cell coverage area corresponding to the serving MeNB to a second cell coverage area corresponding to the target MeNB,
In response, the UE is further configured to determine to handover the UE from the serving MeNB to the target MeNB
eNB.
3. The method of claim 2,
The measurement report includes a reference signal received power (RSRP) or a reference signal received quality (RSRQ)
eNB.
The method according to claim 1,
In order to handover both the UE and the SeNB to the target MeNB,
And to transmit a radio resource control (RRC) connection reconfiguration message to the UE via the wireless transceiver,
Wherein the RRC connection reconfiguration message includes a field indicating a list of cells to maintain in the SCG
eNB.
delete The method according to claim 1,
The processor comprising:
From the SeNB, a response to the command,
Transmits a sequence number status transmission and data forwarding message to the target MeNB,
Further comprising receiving, from the target MeNB, a UE context deactivation message
eNB.
The method according to claim 1,
The serving MeNB is configured to communicate with the SeNB and the target MeNB via a non-ideal backhaul interface X2
eNB. delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete delete

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